Dirty diapers could actually become a cheap and sustainable construction material. As strange as it might sound, discarded diapers can be sterilized and reused in concrete and mortar, new research says. Doing that has the potential to tackle some big environmental problems, such as cutting down on pollution from construction and landfills.
“One baby in a day can [use] four or five pairs of diapers ... you can image the waste diapers can produce in just one country,” says Siswanti Zuraida, lead author of the research published last week in the journal Scientific Reports and a PhD student in architectural engineering at the University of Kitakyushu in Japan.
Zuraida didn’t have to imagine; she used her own baby’s dirty diapers to build a demo house to test the theory. She and her co-authors ultimately found that up to 8 percent of the sand used to make concrete and mortar for a small home could be replaced with rehashed diapers.
She used her own baby’s dirty diapers to build a demo house to test the theory
This is just an early study, so there would be a long way to go before this could be commercialized. But here’s how it might work: first, there would need to be a system for collecting diapers that otherwise would have ended up in a landfill or incinerated. Zuraida couldn’t collect dirty diapers from other households during the pandemic, but fortunately, she didn’t have to look far. She washed and disinfected her daughter’s dirty diapers herself and then left them to cure for 28 days, drying them in the sun. She then enlisted a brother’s help to manually shred them with scissors.
This shows that households in rural or low-income areas could potentially replicate this DIY project on their own, she says. But if this were to scale up, a city would need special equipment to break down the diapers more easily. Sodium chloride can be used to sanitize the materials.
Diapers are mostly made up of plastic and pulp. So rehashing them could be compared to the way plastic bottles are often downcycled into fibers used for carpeting. What’s especially desirable with diapers is that they contain superabsorbent polymer fibers, according to Zuraida. That characteristic could give concrete materials a self-healing quality since the fibers can absorb moisture in a way that might reduce cracking.
The research team tested six different sample building materials containing varying amounts of diapers to see how much could be added without compromising the strength of the material. That’s how they found that diapers could displace up to 8 percent of the sand used to make concrete and mortar in a 36-square-meter home (387.5 square feet). That includes 27 percent of the sand used in concrete columns and beams and up to 40 percent of sand used to make mortar for partition walls.
All in all, that home could divert 1.7 cubic meters (60 cubic feet) of diaper waste from landfills. The study doesn’t calculate how much greenhouse gas emissions that could prevent, but landfills emit a potent gas called methane, and diapers are a major source of plastic waste and pollution. The global construction boom has also triggered a looming sand shortage. These problems have only grown with urbanization and population growth, particularly in Indonesia, where this study was conducted.
“I hope this [research] can empower people ... and help municipalities or countries to treat this kind of waste [as] valuable,” Zuraida tells The Verge.